Collection box and corresponding heat exchanger

ABSTRACT

The invention relates to a collection box ( 1 ) for a heat exchanger comprising a header ( 5 ) having an at least partially rounded shape and comprising:
         a plurality of openings ( 7 ) for the passage of a plurality of heat-exchange tubes ( 3 ) of the heat exchanger, and   a plurality of flanges ( 9 ) surrounding the openings ( 7 ).       

     According to the invention, the header ( 5 ) comprises a plurality of corrugations ( 11 ), and the flanges ( 9 ) are created at the corrugations ( 11 ) of the header ( 5 ) and respectively have a substantially flared shape directed away from the volume defined by the collection box ( 1 ).

The invention relates to a collection box for a heat exchanger,particularly for a motor vehicle. The invention also relates to acorresponding heat exchanger. Such a heat exchanger is, for example,used in a motor vehicle, notably as a radiator for the cooling system,or in high-pressure applications, for example as a condenser for an airconditioning system.

In general, such a heat exchanger comprises a core bundle of tubes andat least one collection box. This collection box is configured to acceptthe ends of the tubes of the heat exchanger.

For that purpose, the collection box generally comprises a header, forexample in the form of a header plate. The collection box generally alsocomprises a cover that fixes to the header plate to close the collectionbox.

The header plate allows the fluid to be distributed to the heat exchangetubes or allows the fluid from these heat exchange tubes to becollected. The header plate is generally made of aluminum and may forexample be produced by stamping.

The header plate generally has a flat bottom.

However, in applications intended to withstand pressure, it is knownpractice for the header to have an at least partially rounded bottom inorder to withstand the pressure. Moreover, the flat-bottomed ordished-bottomed header plate is usually provided with flangessurrounding openings through which the ends of the tubes of the corebundle of the heat exchanger pass.

The openings such as slots are made in the header plate for theintroduction of the tubes, for example with a removal of material or, onthe other hand, without removing material. In the latter case, thematerial is pushed by the tooling towards the inside of the volumedefined by the collection box, thus creating a flange around the openingfor the introduction of the tube. These are referred to as standardflanges.

The flanges make it possible to ensure contact between the tube and theopening in the header plate and to obtain high-quality brazing in thecase of brazed, for example all-aluminum, exchangers.

The tubes are generally inserted into the opening in the same directionas the tooling used to create the flanges around the openings. Theinserted tubes generally extend partially into the collection box inorder to guarantee correct brazing and firm and leaktight assembly. Withcertain solutions, the tubes protrude into the volume forming areservoir for the fluid by almost half the volume of the collection box.

However, having the tubes protruding into the volume defined by theinterior volume of the collection box that forms a reservoir for thefluid creates an internal pressure drop in the fluid circuit. Thisinternal pressure drop entails increasing the pumping power in order tomaintain a certain fluid flow rate.

According to a known solution, a flat-bottomed collection box may haveflanges referred to as reverse flanges which means to say flangesproduced in the opposite direction to the direction of insertion of aheat-exchange tube. The flanges than have a flared shape facing awayfrom the volume defined by the collection box. However, such reverseflanges are only very slightly flared, which in other words means thatthe known reverse flanges define a small entry cone for the insertion ofthe heat-exchange tubes. The entry cone may therefore not be enough toallow the heat-exchange tubes to be inserted simply, and the solutionsknown from the prior art may present difficulties with inserting theheat-exchange tubes into the header.

Because of this difficulty of inserting the heat-exchange tubes into theheader that has such reverse flanges, such a reverse-flanges solutionfor a round-bottomed header is not envisioned in the prior art whereso-called standard flanges take preference.

It is an objective of the invention to propose a collection box thatallows these problems of the prior art to be solved.

To this end, one subject of the invention is a collection box for a heatexchanger comprising a header having an at least partially rounded shapeand comprising a plurality of openings for the passage of a plurality ofheat-exchange tubes of the heat exchanger, and a plurality of flangessurrounding the openings, characterized in that the header furthercomprises a plurality of corrugations, and in that the flanges arecreated at the corrugations of the header and respectively have asubstantially flared shape directed away from the volume defined by thecollection box.

According to one preferred embodiment, the flanges are formed at thecrests of the corrugations facing away from the volume defined by thecollection box.

Such an at least partially rounded box is suited to withstandingpressure in high-pressure applications, and the header with such reverseflanges, namely flanges facing in the opposite direction to the usualdirection of insertion of the tubes, is able to accept the ends of thetubes which, previously, would have projected into the volume defined bythe collection box.

The ends of the tubes therefore no longer open into the volume definedby the collection box. This results in a significant reduction in thepressure drop associated with the flow of a fluid through the tubes ofthe heat exchanger.

In conclusion, by combining an at least partially rounded header with aplurality of corrugations there is enough material to form reverseflanges that are flared enough to facilitate the introduction of theheat-exchange tubes. Specifically, the reverse flanges according to theinvention define a substantially tulip-shaped inlet opening for theinsertion of the heat exchange tubes that is wide enough because of thisaddition of material.

Said collection box may further comprise one or more of the followingfeatures considered separately or in combination:

-   -   the header has at least one wall, the shape of which is        substantially dished towards the outside of the volume defined        by the collection box,    -   the corrugations are formed on the wall,    -   the corrugations respectively have a top height of the order of        30% of the pitch of the tube, this height being sufficient to        form a flange,    -   the flanges respectively have a substantially conical shape,    -   a cone formed by a flange has an angle of the order of 30°,        making it easier at the same time for the plurality of        heat-exchange tubes to be introduced into the header openings        surrounded by the flanges,    -   the flanges respectively have a first width and a second width        greater than the first width, for example of the order of twice        the first width, thus offering an opening that is wide enough to        facilitate introduction of all the heat exchange tubes into the        openings in the header,    -   the first width is substantially equal to the width of a tube        intended to be inserted in the opening,    -   the flanges respectively have two convex substantially flared        edges with the convexity facing toward the outside of the volume        defined by the collection box,    -   the flanges have a height of the order of half the height of a        corrugation,    -   the flanges are thinned with respect to the corrugations on the        header so that the corrugations respectively have a first        thickness and the flanges respectively have a second thickness        smaller than the first thickness of the corrugation,    -   the thinning of the material at a flange is at least greater        than 30% of the initial thickness of the material, or even        locally greater than 50% of the initial thickness of the        material. By thinning the material the flanges can be lengthened        in order to obtain enough of a flare to facilitate the        introduction of the tubes.

The invention also relates to a heat exchanger, particularly for motorvehicles, comprising a heat-exchange core bundle of tubes, the ends ofwhich are fixed to at least one collection box, as defined hereinabove.

This may be a brazed heat exchanger.

As an alternative, it may be a heat exchanger of which the elements thatform the collection box are mechanically assembled to one another.

According to one embodiment, the heat-exchange tubes have a heightcomprised between 0.8 mm et 2.5 mm, preferably between 1.2 mm and 1.8mm.

The pitch of the heat-exchange tubes, which means to say thecenter-distance between two heat-exchange tubes, is, for example,comprised between 5 mm and 10 mm, preferably between 6 mm and 8 mm.

Further features and advantages of the invention will become moreclearly apparent from reading the following description, given by way ofillustrative nonlimiting example, and from studying the attacheddrawings among which:

FIG. 1 is a perspective view of a collection box according to theinvention for a heat exchanger,

FIG. 2 is a partial view in cross section of the collection box of FIG.1 accepting an end of a partially depicted tube of a core bundle oftubes of the heat exchanger,

FIG. 3 is a side view in cross section of the header of FIG. 1,

FIG. 4a is a first perspective view of a header of the collection box ofFIGS. 1 to 3,

FIG. 4b is a second perspective view of the header of the collection boxof FIGS. 1 to 3,

FIG. 5 is a view in transverse section of the header of FIGS. 4a and 4b, and

FIG. 6 is an enlarged view of the header of FIG. 5 accepting ends oftubes of the heat exchanger.

In these figures, elements that are identical bear the same references.

FIG. 1 schematically and in simplified form depicts a fluid collectionbox 1 for a heat exchanger (not depicted), notably in the automotivefield. The heat exchanger may be used in particular as a radiator or asa condenser for a motor vehicle.

In particular, the invention may be applied to a brazed heat exchanger.

The heat exchanger comprises a core bundle of tubes 3. Only one end ofone tube 3 is visible in FIG. 2. The tubes 3 are for example made ofaluminum or aluminum alloy. They are, for example, substantiallyflattened tubes 3.

The collection box 1 is configured to accept at least one end of a tube3 of the heat exchanger, more specifically to accept the ends of amultiplicity of tubes 3 of the heat exchanger (which is notillustrated). Only one end of one tube 3 is visible in FIG. 2.

The collection box 1 for this purpose comprises a header 5. Thecollection box 1 also comprises a cover 6 fixed to the header 5 so as toclose the collection box 1.

The header 5 is, for example, made of aluminum or of aluminum alloy. Thecover 6 for its part may be made of aluminum of aluminum alloy or, as analternative, of plastic.

The cover 6 may be fixed to the header 5 for example by clip-fastening,by brazing or even by crimping.

Furthermore, the header 5 comprises a plurality of openings 7 for thepassage of the ends of the tubes 3.

The openings 7 have, for example, a substantially elongate shape, likeslots.

The ends of the tubes 3 accepted into the openings 7 may then be brazedfor example to the header 5.

According to one embodiment, the heat exchange tubes 3 have a heightcomprised between 0.8 mm and 2.5 mm, preferably between 1.2 mm and 1.8mm.

The pitch of the heat-exchange tubes 3, which means to say thecenter-distance between two heat-exchange tubes 3 is, for example,comprised between 5 mm and 10 mm, preferably between 6 mm and 8 mm.

According to the embodiment illustrated, the header 5 has a wall 8forming a box end. The collection box 1 additionally comprises lateralwalls 8′ connected to this box end 8.

This is a box end 8 of at least partially rounded shape.

According to the embodiment illustrated, the wall 8 forming the end ofthe box, also referred to as the end wall 8, has a shape that issubstantially dished toward the outside of the volume defined by thecollection box 1. Thus, the end wall 8 of the header 5 has a shape thatis substantially concave with respect to the interior volume defined bythe collection box 1 and substantially convex with respect to the corebundle of tubes 3 of the heat exchanger, with the convexity facingtoward the outside of the volume defined by the collection box 1.

As visible in FIGS. 1 to 3, the collection box 1 additionally comprisesa predefined number of flanges 9 formed on the header 5 at the openings7 for accepting the ends of the tubes 3. More specifically, each opening7 is surrounded by a flange 9. The flanges 9 are in this instanceproduced without the removal of material.

The header 5 additionally comprises a plurality of deformations 11. Thedeformations 11 are created at the substantially dished end wall 8 ofthe header 5. The deformations 11 are produced for example in such a wayas to form a regular pattern.

According to the embodiment illustrated, this pattern is made up ofcorrugations or waves 11.

The corrugations 11 may be produced symmetrically with respect to thelongitudinal axis of the end wall 8 of the header 5. The corrugations 11therefore have crests extending alternating on one side and the other ofthe longitudinal axis of the end wall 8 of the header 5. In order words,the corrugations 11 have, for example, a plurality of crests facingtowards the inside of the volume defined by the collection box 1 and aplurality of opposite crests directed away from the volume defined bythe collection box and therefore toward the outside of the collectionbox 1 and toward the core bundle of tubes 3 of the heat exchanger.

The flanges 9, better visible in FIGS. 4a and 4 b, are formed at thecorrugations 11, more specifically at the crests of the corrugations 11facing away from the volume defined by the collection box. Inparticular, the openings 7 are formed by piercing or perforating theheader 5 at the crests of the corrugations 11 facing away from thevolume defined by the collection box, and the flanges 9 are produced bythe material around these openings 7.

In order to be able to have enough material from which to form theflanges 9 at the corrugations 11, the corrugations 11 are created with asufficient height h (cf FIG. 5), for example with a top height h of theorder of 30% of the pitch of the tubes.

The flanges 9 thus formed face away from the volume defined by thecollection box 1, namely toward the core bundle of tubes 3 of the heatexchanger. They are then referred to as reverse flanges 9.

Thus, and referring once again to FIG. 2 and to FIG. 6, when the end ofa tube 3 of the heat exchanger is inserted into an opening 7 surroundedby such a reverse flange 9, this end of tube 3 lies in a zone Z situatedbetween the crests of the corrugations 11 which face toward the insideof the volume defined by the collection box 1 and the level of the boxend 8 of the header 5 but does not protrude into the volume defined bythe collection box 1. The absence of tubes 3 opening into the volume ofthe collection box 1 makes it possible to improve performance in termsof fluid flow.

The flanges 9 have a sufficient height h′ suited to allowing theinsertion of the ends of the tubes 3, for example of the order of halfthe height h of a corrugation 11.

Furthermore, the flanges 9 have a flared overall shape, such as a tulipshape.

More specifically, the flanges 9 respectively have a substantiallyconical shape, for example of angle α of the order of 30° (cf. FIG. 5).

A flange 9 therefore has two flared edges 9 a, 9 b, corresponding to thetwo long edges, joined together by two short edges 9 c, 9 d.

This flared or substantially conical shape facilitates the introductionof the ends of the tubes 3 into the header 5, from outside the volumedefined by the collection box 1 toward the inside of the volume definedby the collection box 1.

The two flared edges 9 a, 9 b for example have a substantially convexshape with the convexity facing toward the outside of the volume definedby the collection box 1.

With reference to FIG. 5, the tulip-shaped flanges 9 respectively have:

-   -   a first width l₁ at the pierced or perforated crest of the        associated corrugation 11 which corresponds to the shortest        width of the flange 9, and    -   a peripheral second width l₂ which corresponds to the greatest        width of the flange 9.

The first width l₁ is substantially equal to or slightly greater thanthe width of a tube 3 intended to be inserted into the opening 7.

The greatest width l₂ defines the opening 7 surrounded by the flange 9for the insertion of the end of a tube 3. The second width l₂ is madewide enough to allow simple and, notably, simultaneous, insertion of theends of all of the tubes 3 of the heat exchanger (which is not depicted)into the openings 7. The second width l₂ is, for example, of the orderof twice the first width l₁ of the flange 9.

Furthermore, the flanges 9 may be thinned with respect to thecorrugations 11 on the header 5. Specifically, with reference to FIG. 6,a corrugation 11 has, for example, a first thickness e₁, and the flange9 has a second thickness e₂ less than the first thickness e₁ of thecorrugation 11.

The flange 9 may just as easily be thinned at the long flared edges 9 a,9 b as at the short connecting edges 9 c and 9 d.

By way of example, the thinning of material is performed at the flange 9and may range beyond 30% or even locally beyond 50% of the initialthickness of the material.

By thinning the material at a flange 9, this flange 9 may be lengthened.

It will therefore be appreciated that a header 5 comprising such reverseflanges 9 facilitates the introduction of the ends of the multiplicityof heat exchange tubes 3 of the heat exchanger simultaneously and simplywithout requiring any special-purpose tooling notably to guide each tube3 into the associated opening 7.

Specifically, the reverse and flared flanges 9 offer enough of anopening for introduction from outside the collection box 1 toward theinside of the volume defined by the collection box 1.

Finally, these reverse flanges 9 allow the insertion of the ends of thetubes 3 without these ends opening into the volume defined by thecollection box 1, thus encouraging the flow of the fluid inside thecollection box 1.

1. A collection box for a heat exchanger comprising a header having anat least partially rounded shape, the header comprising: a plurality ofopenings for the passage of a plurality of heat-exchange tubes of theheat exchanger; and a plurality of flanges surrounding the openings; anda plurality of corrugations, wherein the flanges are created at thecorrugations of the header and respectively have a substantially flaredshape directed away from the volume defined by the collection box. 2.The collection box as claimed in claim 1, in which the flanges areformed at the crests of the corrugations facing away from the volumedefined by the collection box.
 3. The collection box as claimed in claim1, in which the header has at least one wall, the shape of which issubstantially dished towards the outside of the volume defined by thecollection box.
 4. The collection box as claimed in claim 3, in whichthe corrugations are formed on the wall.
 5. The collection box asclaimed in claim 1, in which the corrugations respectively have a topheight of the order of 30% of the pitch of the tubes.
 6. The collectionbox as claimed in claim 1, in which the flanges respectively have asubstantially conical shape.
 7. The collection box as claimed in claim6, in which a cone formed by a flange has an angle of the order of 30°.8. The collection box as claimed in claim 1, in which the flangesrespectively have: a first width ; and a second width two times greaterthan the first width.
 9. The collection box as claimed in claim 8, inwhich the first width is substantially equal to the width of a tubeintended to be inserted in the opening.
 10. The collection box asclaimed in claim 1, in which the flanges respectively have two convexsubstantially flared edges with the convexity facing toward the outsideof the volume defined by the collection box.
 11. The collection box asclaimed in claim 1, in which the flanges have a height of the order ofhalf the height of a corrugation.
 12. The collection box as claimed inclaim 1, in which the flanges are thinned with respect to thecorrugations on the header.
 13. The collection box as claimed in claim12, in which the thinning of the material at a flange is at leastgreater than 30% of the initial thickness of the material.
 14. A heatexchanger for a motor vehicle, comprising a heat-exchange core bundle oftubes, the ends of which are fixed to at least one collection box inaccordance with claim
 1. 15. The heat exchanger as claimed in claim 14,in which the heat-exchange tubes have a height comprised between 1.2 mmand 1.8 mm.
 16. The heat exchanger as claimed in claim 14, in which thepitch of the heat-exchange tubes is comprised between 6 mm and 8 mm.